Wind turbines typically comprise a wind turbine tower and a wind turbine nacelle, which carries the wind turbine rotor having a horizontal axis and the wind turbine generator.
High rotational speeds of the wind turbine nacelle can lead to severe loads on the wind turbine structure, in particular in combination with a rotating wind turbine rotor and wind turbine generator.
Wind turbine nacelle rotation may be limited with a mechanical brake system, which is able to prevent the wind from turning the wind turbine nacelle in an uncontrolled manor.
Furthermore, electrical yaw drives are provided, which may on the one hand pivot the wind turbine nacelle around the vertical axis of the wind turbine tower such that the orientation of the wind turbine rotor follows the wind direction. On the other hand the torque of the electrical yaw drives may be controlled via power converters to limit the rotational speed of the wind turbine nacelle.
However, mechanical brake systems go along with regular maintenance. Power converters may on the one hand get tripped up and on the other hand depend on power provided to them.